1. Field of the Invention
This invention relates to an apparatus for connecting a brake cable from the outside of a brake to a brake lever in the brake. More particularly, it relates to an improved brake cable-connecting apparatus designed to automatically connect the brake cable to the brake lever with a simple snap-in operation.
2. Description of the Related Art
The present Applicant has proposed the above type of a prior art brake cable-connecting apparatus for a drum brake in published Japanese Patent Application Laid-Open No. 10-220506. This prior art brake cable-connecting apparatus will be described with reference to FIGS. 6 and 7. FIG. 6 is a plan view, illustrating a leading-trailing type (LT type) drum brake, while FIG. 7 is a perspective view, illustrating a connecting area around a connected brake cable. This drum brake offers a combination of a hydraulic actuated type service brake and a mechanical actuated type parking brake.
A back plate 10 is fixed to a non-rotatable portion of a vehicle such as a vehicle body. A pair of brake shoes 11, 12 is resiliently mounted on the back plate 10 to be movable relative to the back plate 10 by shoe-holding devices 13, 14. The brake shoes 11, 12 include semicircular shaped shoe webs 11a, 12a, shoe rims 11b, 12b rigidly secured to the shoe webs 11a, 12a on outer circumferential surfaces thereon to form a T-shaped in cross-section, and linings 11c, 12c affixed on outer peripheral surfaces of the shoe rim 11b, 12b, respectively.
Lower adjacent ends of the brake shoes 11, 12 abut against and engaged with an anchor 10a fixed on the back plate 10 by means of rivets, while upper adjacent ends operatively engage with respective pistons of a hydraulic actuated type wheel cylinder 15 rigidly secured to the back plate 10 by means of bolts. The anchor 10a may be a single unitary press-forging including a rectangular shaped portion, supporting the brake shoe 11, 12, and flanged portions, extend over the shoe webs 11a, 12a so as to restrict the lifting of the brake shoes 11, 12. Alternatively, a combination of a rectangular anchor block supporting the brake shoes 11, 12 and a retaining plate superposed thereon may be utilized by securing the two on a protrusion of the back plate 10 by means of rivets.
A mechanical actuated type brake lever 16 is superposed on the shoe web 11a. The brake lever 16 has a base portion 16a rotatably supported by a lever pin 17 at the upper side of the shoe web 11a. A projection 16b protrudes from a rear edge of the intermediate portion of the brake lever 16 and restricts a clockwise movement of the brake lever 16 in FIG. 6 (a retracted position in a clockwise direction in FIG. 6) by abutting against an inner surface of the shoe rim 11b. A free end 16c is folded in a U-shape, thereby forming a cable-receiving groove 16d. The folded free end 16c has a slanted surface 16e, rising in an upper-right direction in FIG. 7 or in a direction in which a cable end 19b is advanced while the after-described inner cable 19a is caused to sag. The slanted surface 16e is formed at an edge of the folded free end 16c and a projection 16f protrudes in an opposite direction in which a brake cable 19 is pulled. A spoon-like guiding portion 16g, guides the cable end 19b to the slanted surface 16e, formed at a main body of the free end 16c in a direction in which the brake cable 19 is pulled.
A strut 18, bridged between an intermediate portion of the brake lever 16 and the brake shoe 12, is positioned adjacent to the wheel cylinder 15 for adjusting a shoe clearance between a brake drum (not shown) and the brake shoes 11, 12.
A brake cable 19, having the cable end 19b fixedly attached to an inner cable 19a at one end thereof, is connected to the brake lever 16 by receiving the inner cable 19a in the cable-receiving groove 16d and by engaging the cable end 19b with an edge of the cable-receiving groove 16d in the opposite direction in which the brake cable 19 is pulled.
A biasing means, slidably housing the inner cable 19a therein and biasing the inner cable 19a, is provided in the brake between an intermediate portion of the inner cable 19a and a rightward portion thereof in FIG. 6. The biasing means is formed by a curved guide pipe 10b and is rigidly secured to the back plate 10 in a state in which an opening of the guide pipe 10b in the brake is oriented toward the guide portion 16g. 
The other end of the inner cable 19a, not shown, is connected to an operating means such as a hand lever, and a portion of the inner cable 19a, exposed to an ambient air outside of the brake, is usually surrounded and protected by an outer casing.
A leaf spring 20 has a base portion rigidly fixed to the brake lever 16 on a planar surface thereof, and a free end 20a bent at a right angle with respect to the planar surface and extending toward the projection 16f. Such an extending end of the free end 20a is spaced apart from the projection 16f by a gap such as to prevent disengagement of the cable end 19b from the brake lever 16 when the inner cable 19a is left slack before cable routing, or otherwise when the cable end 19b is caused to return to its initial position earlier than the brake lever 16 after pulling of the inner cable 19a is released.
A torsion spring 21 provided resiliently between the brake lever 16 and the shoe web 11a has a primarily function to return the inner cable 19a to its initial position, and at the same time acts in an auxiliary manner to return the brake lever 16 to its restrict position.
Upper and lower shoe return springs 22, 23 are stretched between the brake shoes 11, 12, respectively.
The brake operation in the above-described structure will be explained with reference to FIG. 6.
In service braking, when the wheel cylinder 15 is pressurized, the pistons of the wheel cylinder 15 at both ends thereof thrust the upper adjacent ends of the brake shoes 11, 12 in opposite directions. Then, the linings 11c, 12c are brought into frictional engagement with the brake drum (not shown), thereby braking the brake drum.
Now, another brake operation in the parking brake will be explained. When the brake cable 19 is pulled under remote control, the brake lever 16 is pivoted about the lever pin 17 in a counterclockwise direction in FIG. 6; the strut 18 is then moved rightward, thereby thrusting the brake shoe 12 at the right in FIG. 6. At this time, a counteracting force occurs, which thrusts the opposite brake shoe 11 via the lever pin 17. As a result, the linings 11c, 12c are brought into frictional engagement with the brake drum, thereby braking the brake drum.
Now, the brake cable connecting procedure to the brake lever 16 in the above-described structure will be explained.
Grasping the inner cable 19a by hand, the cable end 19b is inserted into the guide pipe 10b from the outside of the brake, and is advanced in a direction biasing from an initial orientation and is brought to the guide portion 16g. If the inner cable 19a is further pushed, the cable end 19b is moved upward on the slanted surface 16e with sagging of the inner cable 19a, and eventually deflects the free end 20a of the leaf spring 20 in moving over the projection 16f. At the same time, the inner cable 19a is caused to spring back to its original linear shape by means of a self-spring force that builds up in the deflected inner cable 19a at the same time. Consequently, the inner cable 19a is automatically received in the cable-receiving groove 16d in engagement therewith. In addition, the cable end 19b is engaged with the edge of the cable-receiving groove 16d in the opposite direction in which the cable 19 is pulled. As a result, the brake cable 19 is connected to the brake lever 16.
However, there are problems associated with the above-described prior art brake cable-connecting apparatus.
Until routing an operating portion of the brake cable (e.g., the side of the vehicle hand lever) is completed, or when the brake cable 19 had been routed with slacking of the inner cable 19a, then there is a likelihood that the inner cable 19a is dislocated from the cable-receiving groove 16d or the cable end 19b is disengaged from the projection 16f, because the cable end 19b is moved in an upward direction in FIG. 6 along the inner surface of the shoe rim 11b. Further, when the pulling of the brake cable 19 is released, then there is again a possibility that the cable end 19b may be disengaged from the projection 16f if the inner cable 19a is caused to return its initial position ago earlier than the brake lever 16.
In order to overcome such problems, the conventional brake cable-connecting apparatus includes the leaf spring positioned in such a manner that a tip of the free end of the leaf spring 20 closer to the cable-receiving groove 16d in order to prevent the inner cable 19a dislocating and the cable end 19b disengaging.
However, since the leaf spring 20 must be provided in a small space, such a layout is difficult to make, with a consequential increase of the components.
Since a relatively great acting force is exerted on the brake lever 16, the brake lever 16 is usually made of either a steel plate or a carbon steel casting, which has a thickness of at least 4 mm. However, in viewpoint of productability and cost, the steel plate is usually pressed-formed into the brake lever 16.
In press-forming the steel plate, the free end 16c of the brake lever 16 is bent into a U-shaped configuration in order to form the cable-receiving groove 16d. At this time, an inner peripheral surface of a groove bottom is contracted, while an outer peripheral surface of the U-shaped portion is expanded, thereby causing excess metal portions at both edges of the groove bottom. As a result, the cable end is unsteadily seated on one such groove bottom edges. This status causes a bending force to be repeatedly imposed on the inner cable 19a in the immediate vicinity of a neck of the cable end 19b, with a concomitant reduction in durability of the inner cable 19a. In addition, removal of the excess metal portions using a grinder requires a lot of time and effort, although the cable end 19b is steadily seated on the groove bottom edge.
The curved guide pipe 10b is employed as a means for biasing the brake cable 19. However, a thick material must be used to form the guide pipe 10b because a biasing force acts on the curved portion of the guide pipe 10b during operation of the brake cable. As a result, the guide pipe 10b is made heavier in weight. In addition, since the guide pipe 10b is fillet-welded to the back plate 10, the back plate 10 may deform by the influence of heat during the welding, thereby consequential reducing in dimensional accuracy of the back plate 10.
In view of the above, an object of the present invention is to provide a brake cable-connecting apparatus for a drum brake, designed to provide easy layout, even with a small space, to permit a cable end to be steadily seated on a brake lever, and to reliably holds a brake cable in position through the aid of a simplified structure, which otherwise would be disengaged from the brake lever.
An aspect of the present invention provides a brake cable-connecting apparatus for a drum brake, including a brake lever positioned over a shoe web of a brake shoe. The brake lever has a proximal end rotatably supported on the shoe web. A biasing means permits the brake cable to be advanced toward a free end of the brake lever. The brake cable is inserted into the brake from the outside of the brake, and a cable end is fixed to the brake cable, the cable end being held against a back edge of the brake lever in a direction opposite to a direction in which the brake cable is pulled. The brake cable is thereby connected to the brake lever, wherein a slanted surface formed at the free end of the brake lever along an outer edge of the free end permits an inner cable to be resiliently deformed while the cable end is slid on the outer edge of the free end when the cable end is advanced to the free end of the brake lever. Furthermore, an opening formed in series with a cable-receiving groove receives the inner cable.
According to another aspect of the present invention, a brake cable-connecting apparatus is provided, wherein an abutment plate is disposed on a main body of the brake lever at a free end of the brake lever, the abutment plate being positioned opposite to the free end of the brake lever, and further wherein the main body of the brake lever and the abutment plate cause both of the cable-receiving groove and the opening to be formed at the free end of the brake lever.
According to a further aspect of the present invention, a brake cable-connecting apparatus is provided, wherein the abutment plate is made of a thin plate, and wherein the abutment plate has a slanted surface defined along an outer edge of the abutment plate, the slanted surface being formed by a bent surface that is bent in a direction in which the bent surface is spaced apart from the main body of the brake lever.
According to a yet further aspect of the present invention, a brake cable-connecting apparatus is provided, wherein the abutment plate is formed with an extension that extends from the bent surface of the abutment plate in a crank-like or stepped manner, and further wherein a groove defined between the extension and the main body of the brake lever has a width large enough to permit the cable end to pass through the groove, but is too small to allow a coiled compression spring to travel through the groove, the coiled spring being wound around the inner cable.
A still further aspect of the present invention provides a brake cable-connecting apparatus, wherein the biasing means for biasing the brake cable is formed by a plate-like member that extends from an anchor portion, the anchor portion supporting the brake shoe.
Another aspect of the present invention is to provide a brake cable-connecting apparatus, wherein the plate-like member is a retaining plate that restrains the brake shoe from floating in a direction parallel to the axis of the brake.
Still another aspect of the present invention is to provide a brake cable-connecting apparatus, wherein a biasing force that acts on the inner cable during operation of the brake cable is supported by a back plate adjacent to the anchor portion, the brake shoe being movably positioned on the back plate.